Tips on Electric Vehicles and Chargers with ENERGY STAR

Gasoline and diesel vehicles are the leading source of carbon dioxide (CO2) emissions in the USA. In addition to CO2, combustion engines release pollutants that cause smog and are harmful to human health.  

The Benefits of Electric Cars 

Electric Vehicles (EVs) benefit the Environment and Public Health  

Charging and operating your car with electricity rather than fossil fuel provides environmental benefits, even after accounting for the emissions from electricity used for charging. Over time, as the electricity grid gets cleaner due to the increase in renewable energy sources, the environmental benefit of EVs will grow even further.    

EVs Save You Money  

Fuel cost savings - Combustion engines are about 20% efficient, meaning that 80% of the burned fuel is wasted as heat. Conversely, electric motors have 90% efficiency, yielding significant fuel cost savings in the long run. A U.S. Department of Energy report concluded that drivers can save as much as $14,500 on fuel costs over 15 years of driving an EV compared to a similar gasoline vehicle. 

Maintenance cost savings: EVs have modest maintenance requirements due to fewer mechanical parts, which reduce or eliminate the need for tune ups, oil changes, and other routine inspections. This can total up to $4,600 of lifetime savings, as highlighted by Consumer Reports.  

Rebates, tax credits, and other incentives: ENERGY STAR certified EV chargers can be eligible for a tax credit of up to 30% on a system that costs up to $1,000 (through 12/31/2021). Keep your receipts for purchase and installation and consult a tax professional for details (IRS Form 9811).   

In addition, there are many state and local incentive programs that can help cover costs associated with the purchase and installation of an EV charger. Enter your zip code into the ENERGY STAR Rebate Finder to see what incentives are available in your area.  

Carpool and HOV Lane Access: In many areas of the country, EV drivers can access HOV lanes, providing an additional benefit for EV owners.  

Charging Your Electric Car 

Type of charger: 120 Volt, or 240 Volt? 

For fully battery electric cars, that are used regularly, a 240 Volt (minimum 30 Amp) charger is recommended. These chargers provide relatively fast charging (e.g., fully charge from empty in 6-8 hours) and can serve nearly all routine needs.   

120 Volt 

(15-20 Amp)

2 to 5 miles of range per  1 hour of charging 

240 Volt 

(30-40 Amp) 

10 to 20 miles of range per  1 hour of charging* 

* Assumes 3.3 kW to 6.6 kW charging power. Charging rates are higher when using more powerful Level 2 chargers, and for EV models rated and wired for 50 Amp. 

Source: EPA Green Vehicle Guide: Plug-In Electric Vehicle Charging  

Best practices for EV charging 

  • Do not fully charge the battery: To maximize battery life, the daily charging should be to approximately 80% of battery capacity.  For occasional use and long trips, charging to 100% is fine, but everyday charging to full capacity can lead to decreased battery life. Another issue with charging to 100% is that the vehicle regenerative braking will not engage, meaning the EV is not running at maximum efficiency.  

  • Avoid extreme heat: If possible, avoid charging in extreme heat. Although battery packs are designed for extreme conditions, it is better to charge during the coolest times of day so that the battery thermal management system does not have to work too hard.   

  • Pre-heat during cold weather: For a fully battery electric vehicle (not a plug-in hybrid) the battery, rather than the hot gas engine, becomes the primary source of heat. When the heater of an EV is engaged in sub-freezing temperatures, the battery capacity will be greatly reduced and will not get full range. Pre-condition the vehicle by turning on the heater while the car is still plugged in and wait several minutes prior to driving while the vehicle is still connected to the charger to maximize range in cold weather. 

  • Charge at the right time of day: Night-time charging is best since the strain on the electric grid is the lowest and electricity rates are lower in some regions. Some areas like California, Arizona, and Hawaii, have large solar farms that put out maximum power during the day, making daytime the best time to charge to minimize costs and environmental impacts. Check with your local utility for guidance on the best times to charge and adjust to those times if you can. Many EV chargers have smartphone apps and network capabilities that allow users to program charging for certain times of day to get the most economical and cleanest power.   

Choose an ENERGY STAR Certified EV Charger  

ENERGY STAR certified EV chargers offer customers: 

  • Energy savings - Like other ENERGY STAR certified products, certified EV chargers save energy when in the standby mode (roughly 85% of the time that they are plugged in), reducing energy waste and charging costs.   

  • Testing and verification - Many manufacturers who sell EV chargers online make false safety and performance claims for their products. All ENERGY STAR certified products are fully tested for safety and energy use, and are verified by nationally recognized independent certification bodies.  

  • Communications network standards -ENERGY STAR EV chargers use industry network communication standards. For the consumers, this means that the chargers are designed to work with a wide variety of other devices (wi-fi routers, electric utility energy management and price signals, etc.). While these communications protocols are still developing, choosing ENERGY STAR today means that you are aligning with emerging industry standards.  

Where to find ENERGY STAR Products 

The ENERGY STAR list of certified EV chargers has now grown to include more than 200 unique models from 17 manufacturers to date and is available on the ENERGY STAR Product Finder.  

Additional guidelines and resources for potential EV charger purchasers are available on the EPA ENERGY STAR’s Electric Vehicle Charger webpage.  

Author: Peter Banwell, ENERGY STAR Certified Products